Color inkjet printers, which are typical printing apparatuses, are already well known. The color inkjet printer has an inkjet type print head for discharging ink from nozzles and is structured to record images, letters, and the like by making ink droplets land onto print paper, which is an example of a printing medium.
Further, the print head is supported on a carriage which is an example of a movable moving member and which is provided with the print head in such a state that a nozzle surface in which the nozzles are formed opposes the print paper, and the print head moves (performs main scanning) in a width direction of the print paper along a guide member and ejects ink in synchronism with the main-scanning.
Further, in recent years, color inkjet printers capable of performing so-called borderless printing in which printing is performed on the whole surface of print paper are gaining popularity for reasons such as that image output results that are the same as photographs can be achieved. With borderless printing, for example, it is possible to perform printing by ejecting ink at the four edges of the print paper with no margins.
=Upper Edge=
It is necessary to accurately ascertain the position of the print paper in order to carry out precise printing at the positions in which dots should be formed on the print paper. One procedure for achieving this is to have the printing apparatus ascertain the position of the upper edge of the print paper.
Several methods have been proposed for ascertaining the position of the upper edge of the print paper, and one of these methods is to emit light from a light-emitting diode or the like, and then to ascertain the position of the upper edge by detecting a change in the output value of a light-receiving sensor such as a photodiode (hereafter, also referred to as a light receiving section) caused by the print paper, which is being fed, blocking the light.
There are cases, however, in which the print paper is supplied (or fed) in a skewed (diagonal) manner; therefore, strictly speaking, the position of the upper edge that has been ascertained by the above-mentioned method may not be the most leading position in the paper feed direction, and a problem may occur with regard to the precision with which the printing apparatus ascertains the upper edge position.
In particular, in the case of borderless printing, it is necessary to accurately ascertain the position of the upper edge of the print paper since printing is carried out on the upper edge of the print paper as well, and if the upper edge position cannot be ascertained accurately, a problem may occur such as a blank portion appearing on an upper portion of the print paper that has been printed. Furthermore, if printing is carried out by enlarging the print area and providing a margin in order to avoid such a problem, then problems such as consumption of excessive ink may occur.
=Lower Edge=
As described above, it is necessary to accurately ascertain the position of the print paper in order to carry out precise printing at the positions in which dots should be formed on the print paper. One procedure for achieving this is to have the printing apparatus ascertain the position of the lower edge of the print paper.
Several methods have been proposed for ascertaining the position of the lower edge of the print paper, and one of these methods is to emit light from a light-emitting diode or the like, and then to ascertain the position of the lower edge by detecting a change in the output value of a light-receiving sensor such as a photodiode (hereafter, also referred to as a light receiving section) caused by the print paper, which is being fed, blocking the light.
There are cases, however, in which the print paper is supplied (or fed) in a skewed (diagonal) manner; therefore, strictly speaking, the position of the lower edge that has been ascertained by the above-mentioned method may not be the most trailing position in the paper feed direction, and a problem may occur with regard to the precision with which the printing apparatus ascertains the lower edge position.
In particular, in the case of borderless printing, it is necessary to accurately ascertain the position of the lower edge of the print paper since printing is carried out on the lower edge of the print paper as well, and if the lower edge position cannot be ascertained accurately, a problem may occur such as a blank portion appearing on an lower portion of the print paper that has been printed. Furthermore, if printing is carried out by enlarging the print area and providing a margin in order to avoid such a problem, then problems such as consumption of excessive ink may occur.
The present invention has been made in view of the foregoing issues, and it is an object thereof to achieve a printing apparatus, a method for determining an upper edge of a medium to be printed, a computer program, and a computer system that are capable of ascertaining, with good precision, the position of an upper edge of a medium to be printed. A further object of the present invention is to achieve a printing apparatus, a method for determining a lower edge of a medium to be printed, a computer program, and a computer system that are capable of ascertaining, with good precision, the position of a lower edge of a medium to be printed.